Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 40

1.6.2 The Source
The term 'source' could do with some further attention. At any contaminated site, a
primary source that is responsible for ongoing contamination of the upper soil layer,
e.g., a leaking pipeline, an oil spill, waste materials stored on the surface of the soil,
must be fully eliminated, when possible. In case of ongoing atmospheric deposi-
tion, elimination of the source often is a long-term political process addressing the
responsible parties for immissions of contaminants, and it is not always possible.
Other sources might be part of agricultural practices, such as the application of fer-
tilizers and pesticides. In that case, an acceptable soil quality would constitute a
harsh boundary condition in agricultural soil management.
Contamination of the upper soil layer, in addition to being a potential cause
of risk to human beings, the soil ecosystem and to Food Safety, is a source for
groundwater contamination. This might lead to the necessity of removal or control
of contaminants in the upper soil layer for the purpose of protecting the groundwater.
1.6.3 Procedures
In the late 1970s, Risk Management was often the same thing as complete removal
of the contaminants and, hence, of the risks involved. Harsh remediation measures,
such as Dig-and-Dump (remediation of the upper soil) and Pump-and-Treat (reme-
diation of the groundwater) were the most popular mechanisms to achieve this goal.
Alternatively, insulation of the contaminants, and hence of the risks involved, was
used as a less strict but cheaper solution. Since the early 1990s, the general focus
of Risk Management has evolved into the elimination of unacceptable risks , which
does not necessarily mean complete removal of the contaminants. Today, the reme-
diation objective is often set at a concentration where the risks for human health,
the soil ecosystem, the groundwater and/or Food Safety relate to an acceptable risk
level .
Moreover, the weighing of the end goal of remediation against necessary costs
has evolved into the common way of performing Risk Management.
The most simple and generally least expensive solution for contaminated site
problems relates to changing the land use, or adapting the layout of the site within
the same land use, in terms of blocking the major exposure pathways. An exam-
ple of change of land use is using cadmium contaminated sites at the border of a
municipality for city expansion, which does not allow substantial vegetable produc-
tion, instead of using it for vegetable gardens or for agricultural purposes. In this
way human exposure through vegetable consumption is reduced or eliminated. An
example of changing the layout of a site within the same land use is given by a lead
contaminated site with a heterogeneous contamination pattern. The human health
risks can be substantially reduced when the buildings are situated on the locations
with the highest lead contents and the bare surfaces (garden and borders) on the
locations with the lowest lead concentrations. In this way exposure of children to